Photosensitive apparatus



June 13, 1939. w DAWSON r AL 2,162,529

' PHOTOSENSITIVE APPARATUS Filed March 12, 1936 2 Sheets-Sheet lWITNESSES: INVENTORS m John IM Dawson and 1 Ed??? H l ddk'.

7 ATTORN Y June 13, 1939.

J. w. DAWSON ET Al. PHO'I'OSENSI'IIVE APPARATUS 2 Sheets-Sheet 2 FiledMarch 12, 1936 MQ N Patented June 13, 1939 UNITED STATES PATENT OFFICEmorosansmva arraaa'ros vania Application March 12, 1936, Serial No.68,474

5 Claims. (01. 209-111) Our invention relates to photo-sensitiveapparatus and has particular relation to inspecting apparatusincorporating photo-sensitive devices.

It is an object of our invention to provide simple and inexpensiveapparatus for classifying articles according to color.

A further object of our invention is to provide photo-sensitiveapparatus incorporating only a simple photo-sensitive device forclassifying articles according to color.

Another object of our invention is to provide photo-sensitive apparatusincorporating only a single photo-sensitive device for dividing articlesinto at least three color classifications.

More concisely stated, it is an object of our invention to provide asimple and inexpensive automatic sorting device that shall operate withprecision and shall require few adjustments and replacements.

, According to our invention, the radiations emitted by the article tobe classified are resolved into a plurality of color components, andimpulses of radiant energy corresponding to the color components areproduced. The impulses are converted into electrical current impulses bya photo-sensitive device and each current impulse is in its turntransmitted through a separate current path. The current impulsesactuate suit able classifying mechanisms.

The novel features that we consider characteristic of our invention areset forth with particularity in the appended claims. The inventionitself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following descriptionof specific embodimentswhen read in connection with the accompanying drawings, in which:

Figure '1 is a diagrammatic view showing an embodiment of our invention;

Fig. 2 is a view in front elevation showing one of the elements utilizedin the practice of our invention in accordance with Fig. 1; and

Fig. 3 is a diagrammaticview showing a modification of our invention.

In Fig. 1, a system is shown which is utilized for the purpose ofclassifying such articles as oranges in accordance with their lightreflecting properties. It may be necessary, for example, to separate theoranges into three color groups, green, yellow and orange. Accordingly,each orange I is disposed on a conveyor 3 and advanced thereby to aregion where it is strongly illuminated by a plurality of suitableilluminating sources 5. While so-called white light is preferably usedto illuminate the orange in the present embodiment of our invention,in,,certain of the modifications of our invention light lacking one ormore of the primary colors or even purely monochromatic light may beused with advantage.

The radiations reflected by the orange I are projected onto a singlephoto-sensitive device I through a disk 9 composed of two semi-circulartransparent segments II and I3, each capable of transmitting a differentcolor. The color of thesegments I I and I3 should correspond to thedesired classification of the oranges, and in the present case onesemi-circular segment I I should transmit green light while the other I3should transmit orange. The disk 9 is rotated by a suitable synchronousmotor I 5 which in its turn is energized from a suitable alternatingcurrent source I1. The speed of the disk 9 is such that each segmentthereof traverses the path of the radiant energy reflected by the orangeI for an interval of time corresponding to a half cycle of the source.

It may be assumed for convenience that during the positive half-cyclethe green segment II traverses the path of the radiant energy whileduring the negative half-cycle the orange segment I3 traverses theradiant beam. The photosensitive device I is accordingly energized by aplurality of alternate pulses of radiant energy one pulse correspondingto the green radiations emitted by the orange and the other pulsecorresponding to the orange radiations emitted by the orange. Thecorresponding current impulses are transmitted through a networkincluding the photo-sensitive device 1, a resistor I9 and a suitablepower source 2I. The resistor I9 is connected at one terminal to thecommon junction point 20 of the cathodes 23 of the discharge devices 25and 21 through a biasing potential source 29 common to both dischargedevices. At the other terminal, the resistor I9 is connected to thecommon junction point 30 of the poles of one polarity of the auxiliarybiasing sources 3|. The remaining poles of the sources 3| arerespectively connected to the control electrodes 33 of the dischargedevices 25 and 21.

The discharge devices 25 and 21 are illustrated as having hot cathodes23. In the practice of our invention, discharge devices may also beutilized which have unexcited cathodes or cathodes of the mercury pooltype. Where the load requirements are small, the discharge devices 25and 21 may, moreover, be of the high vacuum type. In the presentembodiment, the load requirements aremoderately large and we prefer touse gasfilled hot cathode discharge devices.

' The anodes 35 of the-discharge devices 25 and 27 are connected to theterminal taps 31 and 39 of the secondary M of a suitable supplytransformer 53 while the common junction point 29 of the cathodes 23 isconnected to an intermediate tap 45 of the secondary through a suitablecurrentlimiting resistor 61.

It will be seen that the discharge devices 25 and 27 are capable ofpassing current during alternate half cycles of the source ill. Themagnitude of the current transmitted by each discharge device depends onthe magnitude of the control potential impressed thereon and this isdetermined by the current transmitted through the resistor 59 common toboth control circuits and to the photo-sensitive device l while theanodecathode potential is' positive. Accordingly, the current in adischarge device 25 or 21 will depend on the extent of excitation of thephoto-sensitive device 1 during the half cycles when the anodecathodepotential of the discharge device is positive and therefore on theradiant energy trans- -mitted by the corresponding .segment I! or E3 ofthe disk 9 to the photo-sensitive device during the same half cycle. I

For the purpose of illustration, assume that when the top terminal 33 ofthe secondary ll is positive the green segment ll intersects the radiantenergy beam from the orange 1. In such a ase, a current flows throughthe resistor l9 common to the control circuits which corresponds to thegreen light reflected by the orange, while the upper discharge device 25is capable of passing current. If the orange 0 is strongly green, apositive potential of considerable magnitude will be impressed betweenthe control electrode 33 and the cathode 23 of the upper dischargedevice and this discharge device will pass a pulse of current ofconsiderable magnitude which will persist for a half cycle. After thecorresponding half period, the lower terminal 39 of the secondarybecomes positive and the orange segment l3 intercepts the radiantenergy. If the orange i is strongly green, as we have assumed above, thepositive potential which is now superimposed between the controlelectrode 33 and the cathode 23 of the lower discharge device 2? will becomparatively small, and accordingly the lower discharge device willpass only a comparatively small current. The current flowing in onedirection through the secondary M of the transformer 43 and the upperdischarge device 25 is therefore greater than the current flowing in theopposite direction and a corresponding unbalanced condition exists inthe primary circuit 99. Of course, the current through discharge devicepredominates if the orange is strongly orange in color and for theintermediate color, yellow, the current passed by the discharge device25 is substantially equal to that passed by the other discharge device27. In the former case, corresponding dissymmetry is produced in circuit49, and in the latter case, a symmetric state exists in which the netcurrent during any one cycle is zero.

To take advantage of this condition, the exciting coil 5! of a polarizedrelay 53 is connected in the primary circuit 49. The armature 55 of therelay 53 is pivotally mounted on a pin 54 adjacent to the conveyor 3. Itis suspended between springs 51 so that it occupies a central positionwhen the current in exciting coil 5i is symmetric and swings to theright or left in response to dissymmetry in the current in the coil 5!.A chute 59 is rigidly secured to the armature 55 at end adjacent to thepin 54 and extends in a direction at right angles to the longestdimension of the armature. The chute 59 also is pivotal about the pin 59and swings upwardly or downwardly as the armature pivots to the left orright. Assume that the armature 55 swings towards the left when thecurrent in discharge device 25 predominates, as is assumed in the aboveillustration. Under such circumstances, the chute 59 is swung upwardlyand the strongly green orange passes from the conveyor 3 onto chute 59and down chute 59 to a container 6! provided for green oranges. Thearmature swings to the right or takes a central position for the orangeor yellow oranges in the same manner that it pivots to the left forgreen oranges and the oranges are deposited in other containers 63 and55 according to their color. uppermost position should slope downward tofacilitate the movement of the oranges. The polarized relay is providedwith a time delay element which prevents the armature from reverting tothe central position in the time which it takes for the orange i to passfrom its illuminated position to one of the containers 5!, 59, 55.

The apparatus shown in Fig. 1-may be utilized for classifying articleswhere it is desirable that the classification involve only three colorgroups. Let us assume now that the oranges discussed with reference toFig. 1 are to be subdivided into four groups, green, yellow, yellowishorange and reddish orange. To accomplish this object, the apparatusshown in Fig. 3 is utilized.

The oranges i are deposited. in a suitable delivery chute 5'5 and areadvanced through a lateral opening 99 near the bottom of the chute 57onto receptacles 19 provided on a chain conveyor H by the operation ofspokes 33 extending from a rotatable shaft 15 disposed below the chute.'Each orange is advanced by the conveyor H to a region where it isstrongly illuminated by sources of radiant energy 5. In this region, theradiant energy reflected from ,the orange is projected through asectored disk ill onto a photo-sensitive device 7. Since the oranges lare to be classified into four groups, the disk 77 is sub-divided intofour transparent quandrants l9, 8!, 83 and 85 which transmit,respectively, green, yellow, yellowish orange and reddish orange. If theorange is reddish orange in color, radiations of this color reflectedfrom the orange will be transmitted through the corresponding quadrant85 onto the photo-sensitive device '7 while the radiant energytransmitted by the other quadrants will be small. The same principleapplies for yellow, green and yellowish orange articles.

The sectored disk 7'! is rotated at a high speed in synchronism with acommutator 87 by a motor 89. The commutator 81 is provided with aconducting segment 9i over one-quarter of its periphery. The otherthree-quarters are nonconducting. A plurality of brushes 93, 95, 91 and99 corresponding, respectively, to the sectors 79, 8|, 83 and 85 of thecolored disk l1 engage the commutator 81. As the commutator rotates, thebrushes 93, 95, 91 and 99 successively engage the segment 9!. Thecommutator 81 is, moreover, so arranged on its shaft l9! that theconducting segment 9| at any instant cooperates with a brush 93, 95, 91or 99 corresponding to the colored sector 19, 8|, 83 or 85 which, atthat It is to be noted that the chute in its til) instant, is filteringthe radiant energy reflected from the orange I.

The output of the photo-sensitive device 1 on which the reflected andfiltered radiant energy is projected is amplified by a suitabledischarge device I03. When a particular brush (say 99, corresponding tothe reddish-orange sector 05) engages the conducting segment 9|, theoutput current of amplifier I03 is transmitted through a circuitextending from one terminal of a power supply source I05, through aconductor I01 to a common electrical point I09 from which a plurality ofsimilar branches III, H3, H5, H1 extend. Each branch correspondsrespectively to one of the sectors 19, 8|, 83 and 85 and terminates inthe corresponding brush 93, 95, 91 or 99. A relay H9 and a regulatingresistor I 2| is associated with each of the branches III, H3, H5 and H1and the exciting coil I23 of the corresponding relay H9 and thecorresponding resistor I2I are in each case connected in the branchbetween the corresponding brush and the terminal I09.

The current can only continue through the branch III, II3, H5 or II1which provides a conductive path thereto, i. e., through the branchwhose brush 93, 95, Si or 99 is at the instant under observation inengagement with the segment 9I. In the illustrated case, this is thebranch II1 terminating in brush 99. From the segment 91, the outputcircuit of the amplifier I03 extends through a conductor I25 connectingsegment 9I to a conducting ring I21, a brush I29 engaging the ring I21,a plurality of movable contactors I3I in series with each other, whichnormally engage corresponding fixed contacts I33, a conductor Hi l, theanode-cathode discharge path of the amplifier I03, to the other terminalof the power source I05.

Each of the contactors I3I is operable by an armature I35 of one of therelays H9 and when any one of the relays H3 is energized, the outputcircuit of the amplifier I03 is opened at the corresponding contactor I3I In accordance with the magnitude of the radiant energy transmittedthrough a filtering quadrant 19, SI, 83, or 85 of the disk It, a pulseof current is thus transmitted through the coil I23 of the relay II9corresponding to the disk. The relays H9 may beof the inertial type orof the type that responds to an instantaneous current of predeterminedmagnitude. In the former cases. the pulses of current corresponding toeach color are added in the corresponding relay coil I23 as the disk 11and the commutator 81 rotate. Eventually, one of the relays I I 9receives a totality of impulses of such magnitude that it is en-,

ergized and moves its corresponding armature I35. If the relays II9 areof the type instan taneously responding to current of a predeterminedmagnitude, the result is similar. In this case, advantage is taken ofthe fact that the impulses transmitted by each of the relay coilsincreases as the orange I advances under the disk 11 and then decreasesas the orange recedes at a value between the maximum and the minimummagnitudes one relay II9 operates. In both the impulse-relay case andthe last-mentioned case, I

the point at which the relay operates is set by resistors I2I.

The armatures I35 of the relays H9 are each attached to a differenttrapdoor I31 in the chute I39 onto which the oranges I are projected bythe conveyor H. The trapdoors I31 are normally maintained in closedposition by closing springs III and when they are closed the oranges Ipass over them in succession. They are pivoted downward bythe movementof the armatures I35 and provide an opening in the chute I39 throughwhich an orange may drop into a separating chute I43. 4

Accordingly, when one of the relays H9 is actuated the correspondingtrapdoor I31 is opened by the movement of the armatures I35. Thetrapdoor I31 is pivoted downward and is latched in the open position bya latching element I 45 pivotally mounted on one wall of thecorresponding separating chute I43; At the same time, the movablecontactor I 3i of the actuated relay I I9 disengages the correspondingfixed contacts I33 and opens the circuit of the amplifier tube I03 thuspreventing actuation of one of the other relays H9. The orange I whichhas actuated the particular relay H9 is advanced by the conveyor 1! tothe chute I3 and passes down the chute to the opening provided by thetrapdoor I31 which has been opened. It falls through the opening intothe corresponding separating chute I43.

The bottom of the separating chute M3 is also provided with a trapdoorI41 which is opened by the orange as it passes through the chute. Thetrapdoor I51 is mechanically coupled to the latching device I45 by leverI49 and as it opens it disengages the latching device M5 from thetrapdoor I31 in the conveying chute I39, thus permitting thelast-mentioned trapdoor i31 to return to the closed position under theaction of the coil spring MI. The trapdoor I 61 in the separating chuteI43 also carries a movable contact element I5I which engages acorresponding fixed contact element l 53 to close a circuit through theexciting coil I55 of a relay Iii. The armature I59 of the last-mentionedrelay I51 carries a rack IEI. The rack IEI engages a pinion I63rotatable with the shaft 15 on which the spokes 13, whereby the orangesI are ad vanced onto the conveyor II, are mounted and one of the spokes13 advances an orange I onto the conveyor ii. The above process isrepeated for the orange now advanced onto the conveyor.

As has been pointed out, the regulating resistors I2I are utilized forthe purpose of adjusting the operation of the relays H9. To carry outthe adjusting operation, objects having colors corresponding to thestandard desired are advanced on the conveyor and influence thephotosensitive device 1. When one of these objects is advanced, theresistor I2! corresponding to its color is so adjusted that thecorresponding relay H5 is operated when the light reflected from theobject is approximately half of the instantaneous maximum value. Thesame procedure is carried out for the other colors.

It is to be noted that our invention may take a variety of forms and mayhave numerous applications. In particular, attention is called to thefact that while our invention has herein been illustrated as applying toclassify objects according to their radiation reflecting properties, itis equally as well applicable to classification of transparent ortranslucent objects according to their radiation transmitting ordiffusing properties.

Although we have shown and described certain specific embodiments of ourinvention, we are fully aware that many modifications thereof arepossible. Our invention, therefore, is not to be restricted exceptinsofar as is necessitated by the prior art and by the spirit of theappended claims.

We claim as our invention:

1. Apparatus for classifying an object in accordance with its colorcomprising means for projecting a beam of radiant energy on said object,radiant-energy responsive means, means for projecting the resultantradiant energy emitted by said object on said responsive means, meansfor so limiting the radiant energy that the responsive means isinfluenced in cyclic sequence recurring a substantial number of times byselected color components of the resultant radiant energy emitted bysaid object, means to be actuated by said responsive means, when it isinfluenced by said resultant radiant energy for producing periodicallyrecurrent currents which are displaced in phase with respect to eachother and which correspond to said different color components each cycleof said currents corresponding to a complete set of said colorcomponents and means requiring not less than a plurality of cycles ofsaid currents for each actuation thereof for classifying said object inaccordance with the relative magnitudes of said currents during saidplurality of cycles.

2. Apparatus for classifying an object in accordance with its colorcomprising means for projecting a beam of radiant energy on said object,radiant-energy responsive means, means for projecting the resultantradiant energy emitted by said object on said responsive means, meansfor so limiting the radiant energy that said responsive means isinfluenced in cyclic sequence other of said color components, and meansto be actuated in accordance with the relative magnitudes of saidcurrents for classifying said object.

3. Apparatus for classifying an article in accordance with its colorcomprising means for resolving given radiations into its colorcomponents, said resolvhig means operating to provide impulses ofradiant energy corresponding to said color components in cyclicsequence, means for subjecting said article to said resolving means insuch manner that the radiations emitted by said article are resolvedinto a plurality of cycles of radiant energy impulses corresponding tothe color components thereof, said subjecting means including means formoving said article at such a speed that a substantial number of radiantenergy impulses are produced to correspond to each color component, .aplurality of current paths, each current path corresponding to aparticular color component resolved by said resolving means, meansresponsive to the color compong ts of said article for producing currentimpulses in the corresponding current paths and classifying means to beactuated by a plurality of the recurring current impulses correspondingto the color component predominant in said article. 1 I

4. Apparatus for classifying an article in accordance with its colorcomprising means for resolving given radiations into its colorcomponent, said resolving means operating to provide impulses of radiantenergy corresponding to said color components in cyclic sequence, meansfor subjecting said article to said resolving means in such manner thatthe radiations emitted by said article are resolved into a plurality ofcycles of radiant energy impulses corresponding to the color componentsthereof, a plurality of current paths, each current path correspondingto a particular color component resolved by said resolving means, meansresponsive to the color components of said article for producing currentimpulses in the corresponding current paths, means for maintaining saidcurrent impulses in synchro nism with the corresponding radiant energyimpulses, and classifying means to be actuated by a plurality of therecurrent current impulses corresponding to the color componentpredominant in said article.

'5. Apparatus for classifying an article in accordance with its colorcomprising means for resolving given radiations into its colorcomponents, means for subjecting said article to said resolving means insuch manner that the radiations emitted by said article are resolvedinto color components, a plurality of current paths, each current pathcorresponding to a particular color component resolved by said resolvingmeans, means responsive to the color components of said article forproducing periodic currents in the corresponding current paths, aplurality of cycles of current being produced for each component andclassifying means to be actuated by'the currents in said current paths,said classifying means including a relay element in each current path tobe actuated by the current pulses in said path, each of said relayelements being of the type that retains the effect of a current impulseand operates when a totality of current impulses impressed thereonattains a predetermined value.

JOHN W. DAWSON. EDWIN H. VEDDER.

